The present invention relates to a structure for attaching to an engine components necessary for controlling the engine such as a sensor, control unit and the like mounted in an engine compartment, and more particularly to a method of connecting wires for transmitting electric signals between electric circuit devices.
In general, an engine control unit constructed as a microcomputer is placed inside a vehicle where the environmental conditions are comparatively good and sensors and actuators are placed inside the engine compartment of the vehicle, and are connected to a so-called wiring harness for transmitting signals. An example of an electronic control device, such as engine control unit, installed in an engine compartments is described, for example, in Japanese Utility Model Application Laid-Open No. 63-113764 (1988). Therein, a control unit is attached to the outer wall of a throttle body. The main throttle body and a housing for an electronic circuit are formed in one piece, and the electronic circuit is installed inside the housing with the gap between the housing and the electronic circuit being filled with a filler. Since the control unit is placed in the engine compartment, the wiring is extracted through a rubber mount which provides a water-proof connection.
A technology is described in Japanese Patent Application Laid-Open No.4-203437 (1992) where the cooling effect for electronic parts is improved by attaching a control device for a hot wire type air flow meter and the hot wire type air flow meter to an air cleaner body having a one-piece structure. This proposal serves only to cool the electronic parts in the control unit. Similarly, a technology aiming to cool electronic parts is described in Japanese Utility Model Application Laid-Open No. 4-32566 (1992). Therein, electronic parts having high heat generating rates are mounted on boards made of non-organic material and parts having comparatively low heat generating rates are mounted on boards made of organic material to be installed inside an engine compartment.
In the conventional technologies described above, an electronic control device is installed inside an engine compartment and the electronic parts are cooled by utilizing the suction air of the engine. For example, in the case of installing an electronic control device in an air cleaner, the length of the wiring between the components, that is, the length of the wiring harness, is shortened only a little since electric signals have to be transmitted between these components. Therefore, the effect of installing the electronic control device inside the engine compartment is not so large. Further, there is not so large an effect from the point of view of the work required for providing wiring between the components. For example, the total amount of work is not reduced, since work is required for setting the components, for attaching the connectors and for wiring the harness. Furthermore, since the components for engine controlling are connected with wiring harnesses, there are a lot of harnesses running around in the space inside the engine compartment. Further, a break is apt to occur in the wiring due to vibration or repeated contact with an edge of a part or other object. As described above, in the aforementioned conventional technologies, there still remains a significant amount of work and bother in setting components and wiring, and there still is a problem in reliability.